How quickly do decongestants work to relieve symptoms?

Oral decongestants (such as pseudoephedrine and phenylephrine) start working within about 30 minutes and provide relief for 6 to 24 hours (with extended release formulations). Common side effects include irritability, insomnia, heart palpitations, and trembling. If you have any of the following conditions, do not use oral decongestants without checking with your doctor first because they may make these conditions worse: coronary heart disease, high blood pressure, irregular heartbeat, diabetes, glaucoma, hyperthyroidism, enlarged prostate, or problems urinating.

Decongestant nasal sprays (such as phenylephrine and oxymetazoline) provide relief within about 10 minutes and can last up to 12 hours. But nasal decongestants should not be used for more than 2 or 3 days at a time because they may actually cause increased stuffiness with continued use. Common side effects include burning, stinging, or dryness in the nose.

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